Method and apparatus for removing shot from mineral fibre material

ABSTRACT

The invention relates to a method for removing shot from mineral fibres comprising providing a collected web of mineral fibres containing shot, subjecting the collected web of fibres to a disentanglement process, suspending the disentangled fibres in a primary air flow, thereby allowing separation of the fibres from the shot and collecting the fibres, wherein from 0% up to less than 1% by weight binder is present in the fibres collected from the primary air flow.

This invention relates to the treatment of man-made vitreous fibresmaterial so as to reduce the content of shot in the material. Inparticular, the invention relates to the treatment of fibres that arenot subsequently bonded to form a consolidated batt, but are insteadused as loose fibres.

It is standard practice to manufacture man-made vitreous fibres byfiberising a vitreous melt into an air stream which is moving towards acollector and thereby forming a cloud of the primary fibres movingtowards the collector and collecting the fibres of the collector as aman-made vitreous fibre. The fiberisation is usually conducted by theuse of at least one centrifugal fiberising rotor. Often a plurality offiberising rotors is used in the form of a cascade spinner.

In the production of man-made vitreous fibres, it is very common forsignificant amounts of non-fibrous material known as pearls or “shot” toform. In many cases, the shot can constitute as much as 45% by weight ofthe collected mineral material.

The presence of shot with the collected mineral fibres is generallyundesirable, because it hinders the performance of the fibrous material.When the man-made vitreous fibre material is to be used for insulationpurposes, the high shot content can hinder the insulation properties ofthe material. In particular, a high shot content can result in theman-made vitreous fibres being of inadequate quality for use in certainapplications such as acoustic insulation.

The presence of shot can also increase the overall density of theman-made vitreous fibre material, which is disadvantageous in manyapplications.

Whilst the processes for removing shot from mineral fibre material areknown, many of these result inadequate removal of shot. Furthermore,where processes do exist that remove a sufficient amount of the shot,those processes tend to be too uneconomical use in the production ofmany types of product.

Therefore, it is an object of the present invention to provide a processand apparatus that are effective at removing shot from mineral fibrematerial, and which are economical for use in a commercial process.

The present invention is particularly useful for the production ofman-made vitreous fibre material for use in applications where thepresence of some shot can be tolerated, but in which the level of shotnaturally produced in the mineral fibre forming process is too great.For these applications, it is particularly important that the cost ofany subsequent processing of the man-made vitreous fibre material iskept to a minimum in order to ensure that the resulting product iseconomically viable.

The invention relates, in particular, to the production of loose fibresthat are not bonded to each other to form a consolidated batt afterbeing collected. This form of product is often supplied to the customerin the form of bales of fibres and subsequently applied by spraying. Inthis context, it is particularly important to eliminate to as great anextent as possible the presence of large pieces of unfiberised materialfrom the man-made vitreous fibre material.

Therefore, the present invention provides a method for removing shotfrom mineral fibres comprising:

-   -   providing a collected web of mineral fibres containing shot;    -   subjecting the collected web of fibres to a disentanglement        process;    -   suspending the disentangled fibres in a primary air flow,        thereby allowing separation of the fibres from the shot; and    -   collecting the fibres;    -   wherein from 0% up to less than 1% by weight binder is present        in the fibres collected from the primary air flow.

The process of the invention has been found to be effective at removingshot, yet it is highly economical, because, in contrast with many priorart processes, the method and apparatus of the invention can form partof a continuous man-made vitreous fibre production line. This leads tosignificant advantages in terms of the speed of the process and, as aresult, the cost of the resulting product.

According to the present invention we also provide an apparatus forremoving shot from mineral fibres comprising:

-   -   a disentanglement apparatus for disentangling a web of mineral        fibres to provide disentangled fibres,    -   web supply means for supplying the web to the disentanglement        apparatus,    -   air flow supply means for supplying a primary air flow in which        to suspend disentangled mineral fibres,    -   a sifting chamber into which the fibres are carried in the        primary air-flow and in which shot separates from the fibres,    -   a discharge outlet at the lower end of the sifting chamber for        collecting shot separated from the mineral fibres, and    -   a collector for collecting the disentangled mineral fibres,    -   wherein the disentanglement apparatus and the sifting chamber        are separated by a lateral distance of at least 0.5 metres,        preferably from 0.7 to 5 metres, more preferably from 1 to 3        metres.

It has been found that where the sifting chamber is separated from thedisentanglement apparatus in this way, the apparatus can provideparticularly effective shot removal. Separating the location of thedisentanglement process and, where present, the sifting chamber, is alsoa preferred feature of the method of the invention.

As used herein, “shot” is intended to mean vitreous material that is notin the form of elongate fibres. Generally, larger pieces of unfiberisedmaterial are considered to be more disadvantageous for the properties ofthe product than smaller pieces. The invention is particularly usefulfor treating mineral fibre webs containing shot with a maximum dimensionof at least 600 μm. In some embodiments, at least 90 or 95% of the shotof that size is removed. The present invention is also particularlyadvantageous for removing shot with a maximum dimension of over 250 μm.Often at least 70 or 80% of the shot of that size is removed. Theinvention is also effective, however, in the removal of shot with amaximum dimension of at least 63 μm and even in the removal of shot witha maximum dimension of at least 25 μm.

The shot content of the man-made vitreous fibre material treatedaccording to the invention can be reduced significantly. The content ofshot having a maximum dimension greater than 63 μm can be reduced from,for example 40 or 45% by weight to as little as 33%, 25% or even 20%.

The resulting mineral fibre material with a low shot content is suitablefor a number of uses. For example, it can be sprayed with cement onto,for example steel constructions or car park ceilings as insulation.

The invention is also particularly useful for making mineral fibrematerial suitable for marine insulation. In such applications, a lowdensity is of particular importance.

A low shot content is also particularly important for the production ofacoustic insulation. Therefore, the invention is particularly useful inthis context.

According to the process of the invention the man-made vitreous fibrematerial collected from the primary air flow contains less than 1%binder. It is preferred that the man-made vitreous fibre materialcontains less than 0.7% binder and more preferred that less than 0.5%binder is present. Most preferably, essentially no binder is present inthe man-made vitreous fibre material collected from the primaryair-flow.

The material may, and usually does, however, contain other materials inaddition to the man-made vitreous fibres, such as anti-statics and/orlubricants. Specific examples are silanes and processing oil. Theseadditional materials are usually present in an amount less than 1% ofthe total weight of man-made vitreous fibre material collected from theprimary air flow. Usually the amount is less than 0.5% or even less than0.2%.

The man-made vitreous fibres processed in the present invention could beany man-made vitreous fibres, but are usually ceramic fibres or stonefibres. Preferably stone fibres are processed. Stone wool fibresgenerally have a content of iron oxide at least 3% and alkaline earthmetals (calcium oxide and magnesium oxide) from 10 to 40%, along withother usual oxide constituents of mineral wool. These are silica,alumina, alkali metals (sodium oxide and potassium oxide) which areusually present in lower amounts, and also include titania and otherminor oxides.

However, some stone fibres particularly useful in the invention arefibres containing less than 1% by weight iron oxide, around 17-23% byweight, preferably 18-22% by weight silica, a combined level of calciumoxide and magnesium oxide of 34-39% by weight and a maximum combinedlevel of sodium oxide and potassium oxide of 3% by weight.

Fibre diameter is often in the range 3 to 20 microns, in particular 5 to10 microns, as conventional.

As used herein, the term “collected web” is intended to include anymineral fibres that have been collected on a surface, i.e., they are nolonger entrained in air.

The collected web could be a primary web that has been formed bycollection of fibres on a conveyor belt and provided to the process ofthe invention without having been cross-lapped or otherwiseconsolidated. Alternatively, the collected web could be a secondary webthat has been formed by cross-lapping or otherwise consolidating aprimary web. Preferably, the collected web is a primary web.

The disentanglement of the fibres is very important in the presentinvention, because it opens and separates the fibres from each other,thereby releasing the shot that would otherwise remain trapped withinthe web. The disentanglement apparatus is preferably at least one rollerwhich rotates about its longitudinal axis and has spikes protruding fromits circumferential surface. The disentanglement process preferablycomprises feeding the collected web to at least one roller which rotatesabout its longitudinal axis and has spikes protruding from itscircumferential surface

Preferably the roller has a diameter based on the outer most point ofthe spikes of from 20 cm to 80 cm, more preferably from 30 cm to 70 cmstill more preferably from 45 cm to 60 cm and most preferably from 50 cmto 60 cm. The length of the roller is usually from 50 cm to 2 m,preferably from 60 cm to 1.5 m and more preferably from 80 cm to 1.2 m.These dimensions of the roller have the advantage that relatively highspeeds of the outer periphery can be achieved, whilst the size of theapparatus is not prohibitively large.

Rapid rotation of the roller has been found to be particularly effectivein obtaining efficient removal of shot from the fibres. Therefore, inpreferred embodiments the roller rotates at a rate of 500 rpm to 5000rpm, preferably from 1000 rpm to 4000 rpm, more preferably 1500 rpm to3500 rpm and most preferably from 2000 rpm to 3000 rpm.

The high rate of rotation of the roller can result in its outerperiphery travelling at a particularly high speed. According to theinvention, it is preferred that the outer periphery of the roller movesat a speed of from 15 to 200 m/s. More preferably, the speed is from 25to 150 m/s, still more preferably from 40 to 120 m/s and most preferablyfrom 60 to 90 m/s. This speed refers to the speed of the outermostpoints of the spikes. These high speeds have been found to beparticularly effective for removing shot from the mineral fibrematerial.

In some embodiments there are at least two rollers. These rollers mayoperate in tandem or sequentially.

The roller is preferably positioned within a substantially cylindricalchamber. The chamber will have inlets through which the mineral fibresare fed to the roller. The chamber will also have an outlet throughwhich the disentangled mineral fibres are expelled. Preferably, they areexpelled in the primary air flow through the outlet.

In preferred embodiments, the mineral fibres are fed to the roller fromabove. It is also preferred for the disentangled mineral fibres to bethrown away from the roller laterally from the lower part of itscircumference. In the most preferred embodiment, the mineral fibres arecarried approximately 180° by the roller before being thrown off.

The roller preferably occupies the majority of the chamber. Preferablythe tips of the spikes are less than 10 cm, more preferably less than 7cm and most preferably less than 4 cm from the curved wall of thesubstantially cylindrical chamber. This results in the air flow createdby the roller being greater and a more thorough disentanglement of thefibres by the air flow and by the spikes themselves.

According to the invention, the fibres are suspended in a primary airflow. By suspending the man-made vitreous fibre material in a primaryair flow, the more dense shot and heavier chunks of wool can be siftedout as they are influenced by the air flow or flows to a lesser extent,so fall more readily under the force of gravity.

As used herein, the term “air flow” should be understood broadly so asto include not only a flow of air comprising gases in the proportionspresent in the atmosphere of Earth, but also a flow of any suitable gasor gases in any suitable proportions.

The disentangled fibres are generally thrown off the roller in theprimary air flow. In some embodiments, the roller will contribute to theprimary air flow, but usually the rotation of the roller (together withthe fibres being carried on the roller) will be the sole source of theprimary air flow.

Preferably, the primary air flow has an initial speed of 15 to 200 m/s,preferably from 25 to 150 m/s, more preferably from 40 to 120 m/s, mostpreferably from 60 to 90 m/s.

The apparatus of the invention requires air flow supply means forsupplying the primary air flow. This air flow supply means can be formedas part of the disentanglement apparatus. When a spike roller is used asthe disentanglement apparatus, this usually acts for a means forgenerating the primary air flow itself as it creates a flow ofdisentangled mineral fibres suspended in an air flow.

In the method, the primary air flow preferably enters a sifting chamber.In the sifting chamber, turbulence within the primary air flow allowsthe dense particles to be sifted to the bottom of the chamber. It hasbeen found, however, that some separation between the disentanglementapparatus, usually a spike roller, and the sifting chamber can result inimproved shot removal. Therefore, in the method of the invention it ispreferred that the mineral fibres travel for from 0.5 to 5 metres,preferably from 0.7 to 3 metres, more preferably from 1 to 2 metres inthe primary air flow before reaching the sifting chamber.

In the apparatus of the invention, the sifting chamber is separated fromthe disentangled apparatus in the lateral direction by a distance of atleast 0.5 metres, preferably from 0.7 to 5 metres, more preferably from1 to 3 metres.

As the primary air flow enters the sifting chamber there will be asignificant amount of turbulence in the air flow. This is generallydesirable, because it is believed to allow dense particles to be siftedto the bottom of the chamber and promotes further opening of tufts offibres to allow the shot to be released.

The sifting chamber usually includes a discharge outlet at its lower endfor collecting shot that is separated from the fibrous material. Thesifting chamber also usually includes an outlet for the mineral fibresat a higher level than the discharge outlet. Usually, the outlet for themineral fibres is also at a higher level than the inlet through whichthe fibres enter the sifting chamber. Often, the outlet for the mineralfibres is at the upper end of the sifting chamber.

The mineral fibres, when suspended in the primary air flow are, in someembodiments, subjected to a further air flow in a different direction tothe primary air flow. This helps to generate further turbulence in theprimary air flow, which assists in opening the tufts of fibres torelease the shot and allows the fibrous material to be carried in theturbulent air flows, whilst the shot, which is far denser falls underthe force of gravity. Usually the primary air flow is generally lateraland the further air flow is generally upwards. In some embodiments, aplurality of further air flows is provided.

In the apparatus, a further air flow supply means may be present forsupplying the further air flow to the primary air flow. The further airflow supply means, where present, are preferably positioned at the lowerend of the sifting chamber and configured to supply an upwards flow ofair within the sifting chamber. Preferably, there are at least twofurther air flow supply means. In one embodiment, these air flow supplymeans are adapted to deliver a generally upwards further air flow, butare angled towards each other.

The primary air flow supply means are preferably positioned at the sideof the sifting chamber and configured to supply an air flow laterallyacross the chamber.

It has been found that particularly efficient separation of shot fromfibrous material is obtained when a further air flow has a low speed.This is particularly when this is combined with a high speed primary airflow, usually produced by the quickly rotating spike roller. Therefore,it is preferable that the further air flow has a speed of from 0.3 to 10m/s, preferably from 0.5 to 6 m/s, more preferably from 1 to 5 m/s, mostpreferably from 1 to 3 m/s. The further air flow, particularly whendirected in an upwards manner, allows the fibrous material to besuspended for a longer period, particularly in the sifting chamber.However, the low speed of the further air flow or air flows allows themore dense shot to descend to the bottom of the sifting chamber moreeasily. A further air flow in the upwards direction also allows thefibrous material to exit the sifting chamber through an outlet and upperend of the chamber, whilst the shot is collected through an outlet atthe bottom end of the chamber. If the fibres exit the sifting chamberthrough an outlet at the upper end, a low further air flow speed, inparticular within the ranges discussed above, allows the fibres toremain suspended in the sifting chamber for a longer period.

In order to effect a thorough sifting of the fibres, it is preferred toconfigure the apparatus such that the average dwell time of the fibreswithin the sifting chamber is at least 0.5 seconds, more preferably atleast 2 seconds, or even at least 3 seconds.

The sifting chamber can very widely in volume, but it is believed that avolume of from 5 m³ to 20 m³, in particular from 7 m³ to 15 m³ and morepreferably from 8 m³ to 12 m³ gives optimum results in terms of shotremoval.

In a particularly preferred embodiment, after exiting the siftingchamber, the mineral fibres are removed from the air flow in a cyclonechamber.

Optionally, the process may be repeated for further shot removal.

The method may be performed as a batch process, but it is preferred thatthe method is performed at a mineral wool production line. In that case,a primary or secondary mineral wool web can be carried directly afterbeing collected or, as the case may be, cross-lapped into the fibredisentanglement process. This provides a particularly cost efficient andversatile method to remove shot from mineral fibres.

Therefore, the apparatus of the invention preferably furtherincorporates mineral fibre-forming apparatus. This can be any apparatussuitable for that purpose, for example, a cascade spinner. In preferredembodiments, the mineral fibre-forming apparatus is a cascade spinner,which tends to produce a significant amount of shot to be removed. Ineach case, a mineral melt is supplied and fibres are produced by theeffect of centrifugal action of the apparatus.

When a mineral fibre-forming apparatus is included in the apparatus ofthe invention, the apparatus will also include a preliminary collectorarranged to receive the fibres from the fibre-forming apparatus. Theapparatus will also include suction means for applying suction throughthe collector and thereby collecting the fibres on the collector as aweb.

The preliminary collector is preferably in the form of a continuouslyoperated first conveyor belt. The belt is pervious to air. The fibresform a primary web on the belt. Such a means are positioned behind thepreliminary collector to allow an air flow through the collector. Wherethe preliminary collector is a conveyor belt, it can also act astransport means for carrying the collected web towards thedisentanglement apparatus. Otherwise, other transport means may berequired.

The apparatus may optionally comprise means for treating the primary webin any manner known to the skilled person in the art. For example, theapparatus can comprise a pendulum belt for cross-lapping the primary webonto a further continuously operated conveyer belt, to form a secondarymineral fibre web.

In a preferred embodiment, the preliminary collector is in the form of aconveyor belt leading to an inlet duct. The inlet duct may haveconveying rollers at its upper edge to assist with the movement of themineral fibres through the inlet ducts.

Between the preliminary collector (when present) and the disentanglementapparatus, in some embodiments, there is a substantially vertical duct.Often the substantially vertical duct will be narrower at its lower endthan at its upper end.

The invention will be described in the following by way of example andwith reference to the drawings in which;

FIG. 1 is a schematic drawing of an apparatus for removing shot from thefibres.

Apparatus suitable for use in the method in the present invention can beseen in FIG. 1, where a fibre-forming apparatus and preliminarycollector are configured to carry a mineral fibre web to the inlet duct1.

The apparatus comprises an inlet duct 1 for a man-made vitreous fibreweb. At the lower edge of the inlet duct 1, there is a conveyor 2 thatcarries the mineral fibres through the inlet duct 1. As the upper edgeof the inlet duct, conveyer rollers 3, assist with feeding the mineralfibres through the inlet duct 1. At the end of the inlet duct 1, a firstset of mutually spaced elongated elements 4 extend across the end of theinlet duct 1. These serve to break up the larger pieces of the mineralfibre web. In some embodiments, the elongated elements 4 are in the formof rotating brushes that draw the mineral fibres between them as theyrotate.

The mineral fibres that pass through the end of the inlet duct 1 thenfall downwards into a substantially vertical duct 5. In the embodimentsshown, a second set of mutually spaced elongated element 6 extendsacross the upper end of the duct. The second set of elongated elementsis usually more closely spaced that the first. In the embodiments shown,the second set of elongated elements rotate so as to allow sufficientlysmall pieces of the mineral fibres web to pass through, but carry largerpieces away via mineral fibre web recycling duct 7.

The vertical duct 5 generally becomes narrower at its lower end. In theembodiment shown, the lower end of the vertical duct forms the inlet 8to the substantially cylindrical chamber 9. As shown, the inlet 8 is atan upper part of the substantially cylindrical chamber 9. In use, themineral fibre web passes through the vertical duct 5 and through theinlet 8 into the cylindrical chamber 9.

In an alternative embodiment, the vertical duct 5 is omitted. Instead, afeeding mechanism is provided for feeding in a web of mineral fibresdirectly the cylindrical chamber 9. The feeding mechanism may forexample comprise a conveyer belt and optionally one or more feed rollersarranged for controlled advances of the web into the cylindrical chamber9.

A cylindrical chamber 9 has a roller 10 having spikes 11 protruding fromits circumferential surface 12. The roller 10 shown in FIG. 1 rotatesanti-clockwise as shown in the drawing, so that mineral fibres arecarried from the inlet 8 around the left side of the roller 10 as shownand thrown out laterally in a primary air flow into a sifting chamber14.

The spikes may be permanently fixed to the roller for optimum resistanceto wear and tear. For example, the spikes may be fixed by gluing orwelding the spikes in blind holes arranged in the roller outerperiphery. Alternatively, the spikes may be replaceable. This can forexample by accomplished by the roller being a hollow cylinder with holesin the cylindrical wall. The spikes can then for example have a head andbe inserted through the holes through the inside. Hereby spikes can bereplaced if they are broken or worn. Further by having replaceablespikes it is possible to change the pattern of the spikes. Hereby it ispossible to optimise the pattern for different types of material to bedisentangled, e.g. depending on how tightly the mineral fibres arepacked.

In the embodiments shown, the primary air flow is created by therotation of the roller 10 with in the cylindrical chamber 9, and inparticular where the movement of the spike 11 and fibres through thespace between the circumferential surface of the roller and the curvedwall 13 of the cylindrical chamber 9.

The sifting chamber 14 shown in FIG. 1 comprises a discharge opening 16and further air flow supply means 16. In use, shot separates from thefibrous material in the sifting chamber 14 and collects in the dischargeopening 16. The further air flow supply means 15 comprise openingsthrough which the further air flow is supplied. Gauzes 17 are disposedacross the openings of the further air flow supply means 15. Thesegauzes allow the further air flow to pass through into the siftingchamber 14, but are intended to prevent the entry of materials into thesupply means. The further air flow supply means 15 show direct thefurther air flow upwards into the sifting chamber 14.

The further air flow meets the primary air flow containing thedisentangled fibres in the sifting chamber 14. The further air flow hasthe effect of carrying the disentangled fibres upwards within thesifting chamber 14. The more compacted fibres and shot of mineralmaterial will not be carried upwards in the sifting chamber, but fall tothe lower end and the discharge opening 16.

The disentangled fibres are carried to the upper part of the siftingchamber 14 where a removal duct 18 is positioned to carry the mixturefrom the sifting chamber 14. A first air recycling duct 19 is joined tothe removal duct 18 and recycles some of the air from the removal duct18 back to the further air supply means 15.

The removal duct leads to a cyclone chamber 20. The cyclone chamber 20has a second air recycling duct 22 leading from its upper end to furtherair supply means 15. A filter 21 is adjoined to the second air recyclingduct. In the use, the filter 21 removes stray mineral fibres from thesecond air recycling duct 22. As air is removed from the upper end ofthe cyclone chamber 20, the mixture of disentangled fibres and binderfalls through a cyclone chamber outlet 23 at the lower end of thecyclone chamber 20.

A collector 24 is positioned below the cyclone chamber outlet 23. In theembodiments shown, the collector 24 is in the form of a conveyer, whichcarries the collected fibres away to be packaged as bales.

1. A method for removing shot from mineral fibres comprising: providinga collected web of mineral fibres containing shot; subjecting thecollected web of fibres to a disentanglement process; suspending thedisentangled fibres in a primary air flow, thereby allowing separationof the fibres from the shot; and collecting the fibres; wherein from 0%up to less than 1% by weight binder is present in the fibres collectedfrom the primary air flow.
 2. A method according to claim 1, whereinfrom 0% to 0.5% by weight binder is present in the fibres collected fromthe primary air flow.
 3. A method according to claim 1, wherein thedisentanglement process comprises feeding the collected web to at leastone roller which rotates about its longitudinal axis and has spikesprotruding from its circumferential surface.
 4. A method according toclaim 3, wherein the roller has a diameter based on the outermost pointsof the spikes from 20 cm to 80 cm, preferably from 30 cm to 70 cm, morepreferably from 45 cm to 65 cm and most preferably from 50 cm to 60 cm.5. A method according to claim 3, wherein the roller rotates at a ratefrom 500 rpm, preferably from 1000 rpm to 4000 rpm, more preferably from1500 rpm to 3500 rpm, most preferably from 2000 rpm to 300 rpm.
 6. Amethod according to claim 3, wherein the outermost points of the spikesof the roller move at a speed of from 15 to 200 m/s, preferably from 25to 150 m/s, more preferably from 40 to 120 m/s, most preferably from 60to 90 m/s.
 7. A method according to claim 1, wherein the method isperformed at a mineral wool production line, which feeds a primary orsecondary mineral wool web into the fibre disentanglement process.
 8. Amethod according to claim 1, wherein the mineral fibres, when suspendedin the primary air flow, are subjected to a further air flow in adifferent direction to the primary air flow.
 9. A method according toclaim 8, wherein the primary air flow is generally lateral and thefurther air flow is generally upwards.
 10. A method according to claim1, wherein the primary air flow had an initial speed of 15 to 200 m/s,preferably from 25 to 150 m/s, more preferably from 40 to 120 m/s, mostpreferably from 60 to 90 m/s.
 11. A method according to claim 8, whereinthe further air flow has a speed of from 0.3 to 10 m/s, preferably from0.5 to 6 m/s, more preferably from 1 to 5 m/s, most preferably from 1 to3 m/s.
 12. A method according to claim 1, wherein the primary air-flowcarriers the mineral fibres into a sifting chamber.
 13. A methodaccording to claim 12, wherein the fibres are carried in the primary airflow for from 0.5 to 5 metres, preferably from 0.7 to 3 metres, morepreferably from 1 to 2 metres before reaching the sifting chamber.
 14. Amethod according to claim 8, wherein the mineral fibres travel for from0.5 to 5 metres, preferably from 0.7 to 3 metres, more preferably from 1to 2 metres in the primary air flow before meeting the further air flow.15. An apparatus for removing shot from mineral fibres comprising adisentanglement apparatus for disentangling a web of mineral fibres toprovide disentangled fibres, web supply means for supplying the web tothe disentanglement apparatus, air flow supply means for supplying aprimary air flow in which to suspend disentanglement mineral fibres, asifting chamber into which the fibres are carried in the primaryair-flow and in which shot separates from the fibres, a discharge outletat the lower end of the sifting chamber for collecting shot separatedfrom the mineral fibres, and a collector for collecting the disentangledmineral fibres, wherein the disentanglement apparatus and the siftingchamber are separated by a lateral distance of at least 0.5 metres,preferably from 0.7 to 5 metres, more preferably from 1 to 3 metres. 16.An apparatus according to claim 15, wherein further air flow supplymeans are positioned at the lower end of the sifting chamber.
 17. Anapparatus according to claim 15, wherein the sifting chamber has avolume of from 5 m³ to 20 m³, preferably from 7 m³ to 15 m³, morepreferably from 8 m³ to 12 m³.
 18. An apparatus according to claim 16,wherein there are at least two further air flow supply means.